Inorg. Chem. 1991, 30, 4095-4098
4095
Dimethylformamide was distilled from KOH and then from BaO and Contribution from the Laboratoire de Chimie stored over 4-A molecular sieves prior to use in electrochemical experide Coordination du CNRS, 205, route de ments. Narbonne, 3 1077 Toulouse Cedex, France, NMR spectra were obtained on either a Varian XL-200,a Nicolet Instituto Venezolano de Investigationes Cientificas, NT-360,or a GE GN-500 spectrometer. Infrared spectra were obtained Apartado 21 827, Caracas 1020 A, Venezuela, and on a Perkin-Elmer 1600 series FTlR instrument. Electrochemical exGroupement de Recherches de Lacq, ATOCHEM periments were performed on a BAS 100 electrochemical analyzer with (Groupe Elf-Aquitaine), BP 34, 64170 Artix, France glassy carbon working and platinum auxiliary electrodes and a Ag/AgCl reference electrode. Electrochemical solutions were approximately 0.1 Preparation of Novel Low-Coordinate Chloro and Azido P-N M in electrolyte and 0.01 M in analyte. Ultraviolet and visible spectra Compounds. Attempted Synthesis of Cyclodiphosphazenes were recorded on a Hewlett Packard Model 8452 diode-array spectrophotometer. He& Rolland,' Edgar Ocando-Mavarez,* Philippe Potin,t Ru(O)~(C~H~N)~(C~H,O~~) (3). A solution of 1 (0.055 g, 0.17 mmol) Jean-Pierre Majoral,*St and Guy Bertrand*v+ in 25 mL of CH,CIz was cooled to -78 "C. A solution of 3-mercaptopropionic acid (16 pL, 0.18 mmol) in IO mL of CHzClz was added Received November 9, I990 dropwise to the RU(O)~(OH)~(C~H~N),. The reaction mixture was slowly warmed to room temperature with magnetic stirring. A light Introduction green solid precipitated. This solid was collected by filtration, redissolved in pyridine, and precipitated with diethyl ether. The residue was dried Polyphosphazene chemistry is one of the most highly developed under vacuum to give 0.040 g (60%) of the solvated product Ru(O),areas of phosphorus chemistry due to the large range of physical (C5H5N)2(C3H40$)-0.25C5H5N. IR (KBr pellet, cm-I): 802 (RuO,), and chemical properties and to the wide industrial applications 1657 (CO). 'H NMR (CD3CN,360 MHz, 18 "C): 8 7.1-9.0 (m, 12.5 of these inorganic polymers. Various processes lead to the forH, C5H N), 2.88 (t, J = 7.0 Hz, 2 H, CHJ. 2.66 (t, J = 7.0 Hz, 2 H, mation of such polymers, including, for example, the polymeriCH2). I3C(lHINMR ((CD3)30,90 MHz, 35 "C): 8 172.6 (CO), 149.5 zation of cyclotriphosphazenes,' addition of phosphorus penta(py), 136.0 (py). 123.8 (py), 33.9 (CH,), 33.3 (CH,). UV-vis (DMF, chloride to ammonium chloride: polycondensation of N-(di0.0014 M in analyte, nm): A 266 (e = 5333), 308 (4180), 420 (2600), chlorophosphorany1)-P,P,P-trichloro-1X5-phosphazene,3and po580 (2220), 636 (3390). Anal. Calcd for RuC13H14N,04S.0.25C5H5N: C, 41.23; H, 3.70; N, 7.59. Found: C, 41.41; H, 3.94; N, 7.52. lycondensation of monomeric species such as Me3SiN=P(R2)Ru(0)2(C5H4N)2(C4H5N03S) (4). The compound was synthesized OCH2CF3.4 We have shown5 that the photolysis of phosphane according to the method used for 3 in 69%yield from 2 and N-formylazides led to transient phosphonitriles (R,PN), which are in fact L-cysteine. The methylene chloride solvate Ru(0),(C5H5N),(C4H5Nthe monomeric units of polyphosphazenes. Depending on the O3S)CH,CI2 was obtained. IR (KBr pellet, cm-I): 835 (RuO,), 1600 nature of the phosphorus substituents, the phosphonitriles may (CO), 1650 (C-O), 3360 (NH). IH NMR ((CD,),SO, 360 MHz, 18.4 trimerize, oligomerize, and/or In only one case have "C): 6 8.10 (s. 1 H, HCO), 7.6-9.4 (m, 8 H, bpy), 5.60 (s, 2 H, CH,Cl,), 3.15(dd.J=4.4,13.7Hz,l H , C H 2 ) , 2 . 9 5 ( d d , J = 8 . 8 H ~ , 1 3 . 7 H ~ , we been able to isolate and fully characterize a dimer, namely, the tetrakis(diisopropy1amino)cyclodiphasphazene 1 (Scheme I)?& 1 H, CH2), 4.57 (m, 1 H, CH). Anal. Calcd for RuC14H13N305SSince that report, only one other synthesis of 1 has been published? CH2C1s C, 34.56; H, 2.90, N, 8.06; CI, 13.6. Found: C, 34.76; H, 3.14; N, 8.03; CI, 13.53. It also involves the dimerization of a phosphinonitrene, but the Ru(0)2(C5H5N)2(C5H7N03S)(5). In a typical procedure. a solution precursor, the nitrilimine 2, is not readily available, making this of N-acetylcysteine (0.027 g, 0.16 mmol) in 5 mL of DMF was added new route of no synthetic utility (Scheme I). All attempts to dropwise over a period of 15-20 min to a solution of 1 (0.052 g, 0.16 prepare other isolable dimers mmol) in 35 mL of DMF and 5 mL of CHzCI,. The reaction mixture Although several hundred cyclotri-, cyclotetra-, and cyclowas allowed to stir for an additional 1 h at room temperature. A dark polyphosphazenes are known! 1 is, surprisingly, the only example green solid was precipitated by the addition of diethyl ether and was of a cyclodiphosphazene reported so far. This type of fourfiltered out and dried under vacuum to give the product as a CH,CI,/ membered ring is of great importance, since it may shed new light in 70% DMF solvate Ru(0)2(C5H5N),(C5H,N03S)~CHzClz~2DMF on the question of equilibria among monomers, rings, and chains yield. IR (KBr pellet, cm-I): 3272 (NH), 1655 (CO), 1602 (CO), 800 (RuO,). 'H NMR ((CD3),S0, 360 MHz, 30 "C): 6 8.25 (d, J = 7.7 in phosphazenes. Such equilibria could be important in underHz, 2 H, py), 7.90 (s, 2.5 H, CHO), 7.76 (t, J = 7.7 Hz, 2 H, py), 7.37 standing the formation of commercial phosphazene resins. The (t, J = 6 Hz, 2 H, py), 5.65 (s, 2 H, CH,CI,), 4.45 (m, J = 4.3 Hz, 1 development of the chemistry of cyclodiphosphazenes has been H , C H ) , ~ . I ~ ( ~ ~ , J = ~ . ~ H 1ZH,CH&,2.87(dd,J=9.0 ,I~.~HZ, hindered by the lack of large-scale multigram syntheses of these Hz, 13.5 Hz, 1 H, CHz), 2.80 (s, 7.5 H, NCH3), 2.65 (s, 7.5 H, NCH3), compounds. Here we report our attempts to prepare new cy1.83 (s, 3 H, CH,). I3C(IH)NMR ((CD3),S0, 125.7 MHz, 30 "C): 8 clodiphosphazenes via an intramolecular Staudinger reaction, 171.9 (CO), 169.2 (CO), 149.4 (py), 136.0 (py), 123.7 (py), 57.0 (Cstarting from derivatives of type A. HZCI,), 51.7 (CH), 22.2 (CH,). UV-vis (DMSO, 0.001 72 M in analyte, nm): A 266 (e 710), 336 (488), 388 (686), 658 (405). FABMS: m / z 453, (M + H)'. Anal. Calcd for RuC15Hl,N305S~CH,CI,.2DMF C, 38.66; H, 4.87; N, 10.25;CI, 10.37. Found: C, 38.30 H, 4.63; N, 10.55; CI, 10.53. RU(O)~(C~H,N)~(C~H~NO~S) (6). This compound was synthesized Experimental Section according to the method used for 5 from 2 and N-acetyl-L-cysteine. The All experiments were performed under an atmosphere of dry argon. product was isolated in 87% yield as the methylene chloride solvate Melting points are uncorrected. 'H and 13CNMR spectra were recorded Ru(~)~(C~H~N)~(C~H~NO~S)~CH~C~~. IR (KBr pellet, cm-I): 3267 on a Bruker AC80 or a Varian EM 360V spectrometer. 'H and I3C (NH), 1666 (CO), 1600 (CO), 833 (Ru02). 'H NMR ((CD,)ZSO, 360 chemical shifts are reported in ppm relative to Me,Si as internal standard. MHz, 18.0 "C): 6 9.40 (d, 2 H, bpy), 8.50 (t, 2 H, bpy), 8.10 (d, 2 H, 'IP NMR spectra were obtained on a Bruker AC80 spectrometer at 32.43 bpy), 7.60 (t, 2 H, bpy), 5.60 (s, 2.2 H, CH,CI,), 4.48 (m, 1 H, CH), MHz. Downfield shifts are expressed with a positive sign, in ppm, rel3.1 1 (dd, J = 4.6 Hz, 14 Hz, 1 H, CHz), 2.90 (dd, J = 9.0 Hz,14 Hz, ative to external 85% H$O.+. Infrared spectra were recorded on a 1 H, CH2). I3C('H)NMR ((CD3)$0, 125.7 MHz, 30 "C): 6 172 (CO), Perkin-Elmer 983 G spectrophotometer using a polystyrene film for 170 (CO), 159.8, 154.2, 137.3, 126.8, 123.4 (bpy), 57.0 (CH2C1,), 52.0 calibration. Mass spectra were obtained on a Nermag RIO-IOH in(CHI, 22.0 (CH,). UV-vis (DMSO, 0.001 23 M in analyte, nm): A 249 strument. Photochemical reactions were performed in quartz tubes with (e 3090). 412 (1170). 586 (245), 666 (1.40). FABMS: m / z 451, (M a Rayonnet photochemical reactor. + H)'. Anal. Calcd for Ru(C15H15N305S)CH,C1,:C, 35.56; H, 3.19; Synthesis of [(Dicbloropbosphanyl)imino]chlorobis(diisopropylN, 7.73; CI, 14.34. Found: C, 35.68; H, 3.22; N, 7.91; CI, 14.33. amino)phospbornne (5). To a solution of IO g (28.3 mmol) of [(trimethylsilyl)imino]chlorophosphorane 3 in dichloromethane (30 mL), Acknowledgment. We gratefully acknowledge the National maintained at -70 OC, was added dropwise a solution of 3.9 g (28.4 Institutes of Health (Grant PHS 1 R01 A12 8851-01) for financial support of this work. Spectra were obtained on N M R instruments purchased with grants from the National Institutes of Health and 'CNRS. the National Science Foundation ( N I H PHS 1532135, N I H Instituto Venezolano de Investigationes Cientificas. 1531957, and N S F C H E 85-14500). ATOCHEM.
*
0020-1669/91/1330-4095$02.50/0
0 1991 American Chemical Society
4096 Inorganic Chemistry, Vol. 30, No. 21, 1991 Scheme I
R
-
Notes washed three times with acetonitrile at -30 OC and 8 (0.4% g, 60% yield) was obtained as a white powder, only stable at low temperature (-30 'C), "P NMR (C6D6): 20.0 (d), 120.9 (d), Jpp = 171.6 Hz. 'H NMR (C6D6): 0.54 (d, J ~ H 1.4 HZ, 36 H, SiCHJ, 1.21 (d, JHH 6.2 Hz, 12 H, CHI), 1.29 (d, JHH = 6.2 Hz, 12 H, CHI), 3.90 (m, 4 H, CH). Mass spectrum: m/e 631 (Mt), 588 (M+ - iPr), 523 (M+ - MelSiCI).
2 iPr2N
Synthesis of [(Diphenylphosphrnyl)imino)fblorobis(dli~propylemino)pbospborane (IO). A solution of phenyllithium (10.46 mmol) in ether (20 mL) was added dropwise to an ether solution (30 mL) of 5 (2 g, 5.23 mmol) maintained at -70 'C. The resulting mixture was stirred at room temperature for 2 h. After filtration and removal of the solvent
-Rz:CN S
mmol) of trichlorophosphanein 5 mL of dichloromethane. The mixture under reduced pressure, the residue was washed twice with 10 mL of acetonitrile and 10 (2.02 g, 83%yield) was obtained as a white powder. was stirred at room temperature for 2 h. After evaporation of the solvent, I'P NMR (CDCI]): 18.7 (d), 42.3 (d), Jpp 147.7 Hz. 'H NMR the residue was washed with 5 mL of acetonitrileat 0 'C. Filtration and drying under vacuum afforded 5 (9.4 g, 87%yield) as a white powder. (CDCIy): 1.09 (d, JHH= 6.8 Hz, 12 H, CHI), 1.12 (d, J H H 6.8 Hz, Mp: 42-43 'C. "P NMR (C6D6): 172.6 (d), 7.1 (d), Jpp 38.7 Hz. 12 H, CH3), 3.51 (m, 4 H, CH), 7.30 (m, IO H, C6H5). 'IC NMR (CDCI,): 24.00-25.09 (m, CH3CH), 49.6 (d, Jpc = 8.1 1 Hz, CHCH]), 'H NMR (C6D6): 1.07 (d, JHH= 7.0 HZ, 12 H, CHo), 1.16 (d, JHH = 129.67 (s, pC), 129.88 (d, Jpc = 5.24 Hz, m-C), 131.93 (d, Jpc = 13.5 7.0 Hz, 12 H, CH,), 3.37 (m, 4 H, CH). Anal. Calcd for Hz, PC), 133.28 (d, Jpc = 22.57,o-C). Anal. Calcd for CUH18CINlP2: Cl2HzCl3N1P2:C. 37.65; H, 7.32; N, 10.98. Found: C, 37.70 H, 7.28; N, 10.96. C, 61.87; H, 8.16; N, 9.02. Found: C, 61.98; H, 8.09; N, 8.94. of [ ( D i c ~ ~ p h s n y l ) i m i w l u i d o b l s ( d i i r o p ) Syntbcds of I I ( D i ~ r o p y l r m i n o ) ~ ~ ~ n y l p m i n o ~ h l o r ~ i s ( d i Syntbesii i~ pbpborane (12). To a solution of 1.08 g (2.99 mmol) of [(trimethylpmpylamlno)~borane(6). An ethereal solution (30 mL) of lithium silyl)imino]azidobis(diisopropylamino)phosphorane 1158*c in 8 mL of diisopropylamide( 1 .I2 g. 10.48 mmol) was added dropwise, at -70 OC, dichloromethane, maintained at -70 OC, was added dropwise 0.410 g to an ethereal solution (20 mL) of 5 (2 g, 5.23 mmol). The deep orange mixture obtained was stirred at room temperature for 2 h. After filtra(2.99 mmol) of trichlorophosphine. The mixture was stirred at room temperature for 2 h. After evaporation of the solvent and of the trition and evaporation of the solvent, the residue was dissolved in 5 mL methylsilyl chloride, the residue was washed with 3 mL of acetonitrile of dichloromethane. A precipitate was obtained by addition of acetoat 0 OC and 12 (0.683 g. 59%yield) was obtained as a white powder. IlP nitrile. After filtration, two additional washings at 0 OC with IO mL of NMR (C6D6): 3.9 (d), 165.2 (d), Jpp = 21.0 Hz. 'H NMR (CDCl,): acetonitrile, and drying under vacuum, 0.74 (35 96 yield) of 6 was isolated as a white slightly deliquescent solid at room temperature. IlP NMR 1.23 (d, JHH= 7.0 Hz, 12 H, CHI), 1.30 (d, J H H 7.0 Hz, 12 H, CH3), 3.50 (m, 4 H, CH). IR (KBr): 2150 cm-I (N3). Mass spectrum: m / e (CD2CI2): 41.4 (dd, JPH 217.7 Hz, Jpp = 117.7 Hz), 1.9 (d, Jpp 388 (M'), 353 (M' - (21). Anal. Calcd for C12H&12N6P2: c, 37.02; 117.7 Hz). 'H NMR (CD2C12): 1.24 (m, 36 H, CHp), 3.49 (m, 6 H, H, 7.19; N, 21.59. Found: C, 36.72; H, 7.04; N, 21.68. CH), 6.65 (dd, JPH 217.7 and 34.7 Hz, 1 H, PH). 'IC NMR (CD2CI2): 22.16-24.24 (m, CHI), 47.29 and 47.35 (d, Jpc = 5.3 Hz, Synthesis of [ [ ( D i i s o p r o p y l a m i n o ) c ~ ~ ~ n y l ] i m CH), 50.43 (d, Jpc 10.6 Hz, CH). Mass spectrum: m / e 412 (M+), (diisopropylamino)phphorane (16). Diisopropylamine, 0.698 g (6.9 mmol), was added dropwise to a toluene (15 mL) solution of [(di369 (M+ - iPr). 312 (Mt - NiPr2). chlorophosphany1)imino]azidobis(diisopropylamino)phosphorane (12), synthesis of [[(Misopropyhmiw)cbloropboaph.nyl~mino]ehrobis1.345 g (3.45 mmol), maintained at -30 OC. The resulting mixture was (dUropropylrmino)phos*ne (7). To a solution of 3.82 g (IO mmol) allowed to warm to room temperature and was then stirred for 2 h. After of [(dichlorophosphanyl)~m~no]chlorobis(diisopropylamino)phosphorane filtration on Celite and evaporation of the solvent, the residue was washed (5) in toluene (I5 mL), maintained at -30 'C, was added dropwise 2.02 twice with pentane (2 mL), and 16 (1.36 g, 87%yield) was obtained as g (20 mmol) of diisopropylamine. The resulting mixture was allowed to a white powder. Mp: 76 "C. IIP NMR (C6D6): 11.1 (d), 175.5 (d), warm to room temperature and was then stirred for 2 h. The mixture Jpp = 139.2 HZ. 'H NMR (C6D6): 1.08-1.27 (m, 36 H, CHI), 3.35 (m, was filtered through Celite and the solvent removed under vacuum. The 6 H, CH). IR (KBr): 2149 cm-' (P-N,). Anal. Calcd for residue was washed with acetonitrile( 5 mL) and then twice with pentane (5 mL). The product was then dried under vacuum, affording 7 as a C18H42C1N7P2: C, 47.63; H, 9.26; N, 21.61. Found: C, 47.54; H, 9.20; N, 21.78. white powder (3.49 g, 78%yield). Mp: 108 OC. "P NMR (C6D6): 11.8 Synthesis of U(Dlmethyiuniw)chlorophosphmylmiao]rzi (d), 162.7 (d), Jpp 161.8 Hz.'H NMR (C6D6): 1.15-1.35 (m, 36 H, propylamino)phoapborane (17). (Dimethylamino)dichlorophosphane, CHI), 3.50 (m, 6 H, CH). 'IC NMR (c6D6): 21.70-22.84 (m, a $ ) , 0.153 g (1.05 mmol), was added dropwise to a solution of [(trimethyl47.42 (d, Jpc = 5.2 Hz, CH), 47.75 (d, Jpc = 4.9 Hz, CH). Anal. Calcd for C18H12C12N4P2: C, 48.32; H, 9.40; N, 12.52. Found: C, 48.12; H, silyl)imino]azidobis(diisopropylamino)phosphorane, 0.378 g (1.05 mmol), 9.36; N, 12.68. in dichloromethane (8 mL) at -70 'C. The resulting mixture was stirred Synthesis of [[Bl~bis(Mmetbylsilyl)amino]phospbrayl~mino)fblorofor 2 h at room temperature. After evaporation of the solvent and trimethylchlorosilane,0.393 g (94%yield) of 17 was obtained as a slightly bis(diAsopropyhino)phospborrw (8). To an ether solution (6 mL) of 0.44 8 (2.62 mmol) of the lithium salt of bis(trimethylsi1yl)amine at -70 yellow viscous liquid. "P NMR (C&.): 11.8 (d), 181.8 (d), Jpp = 116.7 'C was added dropwise 0.501 g (1.31 mmol) of 5. The mixture was Hz. 'H NMR (CD2C12): 1.20 (d, JHH= 7.0 Hz, 12 H, CHJCH), 1.27 stirred for 2 h at room temperature. According to IIP NMR spectros(d, JHH= 7.0 Hz, 12 H, CHICH), 2.57 (d, 13.0 Hz, 6 H, CHIN), 3.50 copy, a mixture of 8 (90%) and 9 (10%) was obtained. The minor (m, 4 H, CH). IR (CH2CI2): 2151 cm-I (P-N,). Anal. Calcd for compound, 9, was characterized by NMR with comparison an authentic CI4H3&1N7P2:C, 42.26; H, 8.55; N, 24.65. Found: C, 42.30; H, 8.35; sample9 After filtration and evaporation of the solvent, the residue was N, 24.50. Synthesis of the [[(D i a U r y l a m i w ) p b o ~ ~ n o ~ z i ~ s ( d i i s ~ propylrmino)pbogpboranylT r i f l " e t h t e s (19, 20). To a solution of [[(dialkylamino)chlorophosphanyl]imino]azidobis(diiso( I ) (a) Allcock, H. R.; Kugel, R. L. J. Am. Chem. Soc. 1%5,87, 4216. propy1amino)phosphorane 16 or 17 (1.73 mmol) in dichloromethane (7 Allcock, H. R. Angew. Chem., Inf.Ed. Engl. 1977, Id, 147. mL), maintained at -70 OC, was added dropwise 1.80 mmol of tri(2) Hornbacker. E. D.; Li, H. M. US. Patent 4 198 381, 1978. methylsilyl trifluoromethanesulfonate. The resulting mixture was allowed (3) (a) De Jaeger, R.; Heloui, M.;Puskaric, E. French Patent 2466435, 1981. (b) Heloui, M.; De Jaeger, R.;Puskaric, E.;Heubel, J. J . to warm to room temperature and was then stirred for 2 h. After Makromol. Chem. 1982, 183, 1 1 3. evaporation of the solvent and trimethylchlorosilane,phosphenium salts (4) (a) Wisian-Neilson, P.; Neilson, R. H. J. Am. Chem. SOC.1980, 102, 19 and 20 were obtained as slightly yellow oils. 1 9 ItP NMR (C6D6) 2848. (b) Wisian-Neilson, P.; Neilson, R. H. Chem. Rev. 1988,88,541. 22.9 (d), 309.5 (d), Jpp= 87.2 Hz; 'H NMR (CD2C12)1.13-1.30 (m. (5) (a) Sicard, G.; Baceiredo, A.; Bertrand, G.; Majoral, J. P. Angew. 36 H, CHg), 3.45 (m,6 H, CH). UI: "P NMR (c&)20.53 (d), 294.29 Chem.. Int. Ed. Engl. 1984.23.459. (b) Baceiredo, A.; Bertrand, G.; (d), Jpp = 80.5 Hz. 'H NMR (CDZCIZ) 1.25 (d, J H H 7.0 Hz, 12 H, Majoral, J. P.;Sicard, 0.; Jaud, J.; Galy, J. J . Am. Chem. Soc. 1984, CHICH), 1.32 (d, J H H 7.0 Hz, 12 H, CHJH), 2.65 (d, 13.0 Hz, 6 106. 6088. (c) Baceiredo, A.; Bertrand, G.; Majoral, J. P.; El Anba, H, CH,N), 3.55 (m, 4 H, CH). F.: Manuel, G. J . Am. Chem. Soc. 1985. 107, 3945. (d) Biwke, J.; Niecke, E.; Ocando, E.;Majoral, J. P.; Bcrtrand, G. Inorg. Chem. 1986, Heating of [[(DiisopropylPmino)chlorophosphonyl]iminol(di25, 2695. isopropy1amino)phosphorane (16). A 1.610-g sample (3.55 mmol) of (6) Granier, M.; Baceiredo, A.; Dartiguenave, Y.; Dartiguenave. M.: Menu, azidophosphorane 16 in 30 mL of toluene was heated at 1 IO OC with M. J.: Bertrand. G. J . Am. Chem. Soc. 1990. 112. 6277. -. -stirring for 3 h. It could be seen from the I'P NMR spectrum that the (7) Barendt, J.; Bent, E.G.; Haltiwanger, R. C.; Norman, A. D. Inorg. I
Chem. 1989, 28, 2334. (8) Allcock, H. R. Phosphorus-Nitrogen Compounds; Academic Press: New York and London, 1972.
(9) Bijske, J.; Niecke, E.;Nieger, M.; Ocando, E.;Majoral, J. P.; Bertrand, G. Inorg. Chem. 1989, 28, 499.
Inorganic Chemistry, Vol. 30, No. 21, 1991 4097
Notes Scheme I1
Scheme IV IPrzN, 'D
-
SIMe3
u'
Scheme I11
5 PtlJ
N3
Imain products were polymeric (-80%) whereas cyclodiphosphazene18 was formed in a yield of only 20%. After removal of the solvent in vacuo, the residue no longer exhibited the characteristicinfrared absorption band of the azido group (P-N,). All attempts to isolate 18 in pure form were unsuccessful. NMR (C6D6): 52.2 (d), 41.6 (d), Jpp 71.8 HZ; complex multiplet centered at 0 ppm.
Results and Discussion The first problem in our strategy was to synthesize the starting phosphane-iminophosphorane azides of type A. W e first tried to prepare the corresponding chloride by treatment of chloroiminophosphorane 3 with the bis(diisopropy1amino)chlorophosphane in order to obtain a precursor 4 of the known cyclodiphosphazene 1. Even on heating, however, no reaction was observed, and in fact, 3 does not appear to react with monochlorophosphanes. In contrast, a dichloromethane solution of 3 did react with trichlorophosphane, affording the desired phosphane-iminophosphorane complex 5, in nearly quantitative yield (Scheme 11). Since lithium diisopropyl amide is known to substitute chlorophosphane, we attempted the reaction of 5 with LDA. We did not obtain the totally substituted product 4 but a novel phosphane 6. The 31PN M R spectrum of 6 gave a signal in the form of a doublet of doublets at 41.4 ppm (A3-P,JPH= 217.7 Hz, Jpp= 117.7 Hz)and a doublet at 1.9 ppm (A5-P,Jpp= 117.7 Hz). The proposed structure was confirmed by ' H and "C N M R as well as mass spectroscopy. T o rationalize the formation of 6,it seems reasonable to postulate that a chlorine substitution first occurred, giving 7, followed by a lithium-chlorine exchange and subsequent hydrolysis, giving 6 (Scheme 111). In order to provide further evidence for the proposed mechanism, we first prepared 7 by addition of 2 molar equiv of diisopropylamine to 5. The monoamino-substituted product 7 was then characterized by I3C, 'H,and 31PN M R spectroscopy together with elemental analysis. The addition of LDA to 7 in ether at -78 OC was monitored by 31PN M R spectroscopy, and two signals which are believed to correspond to the lithio derivative (73.15 (d), 8.17 (d), Jpp= 134.6 Hz) were observed. However, this extremely water-sensitive compound was seen to rapidly transform, giving 6. In contrast, treatment of 5 with lithium bis(trimethylsily1)amide led to the expected substituted derivative 8, as the major product (90%), along with a small amount (10%) of diazadiphosphetidine 9. Formation of the four-membered ring 9, already obtained in the reaction of bis(diisopropy1amino)phosphonitrile with [bis(trimethylsilyl)amino][(trimethylsilyl)imino] phosphane, probably involves a multistep mechanism? When 2 equiv of phenyllithium was added to 5, a straightforward reaction occurred, leading to the substituted phosphane-iminophosphorane complex 10, isolated in 83% yield. Unfortunately, we were not able to substitute the chlorine atom of 8 or 10 with an azido group. Steric hindrance due to the diisopropylamino groups is probably responsible for the lack of reactivity of these compounds (Scheme IV). Therefore, the synthetic pathway to the target molecule R2P(N,)=NPR', from R2P(C1)=NPC12 implies the following contradiction: the steric hindrance of the substituents R must be sufficient enough to prevent the substitution reaction with the lithium salt at the tetracoordinated phosphorus, but must also be weak enough to allow the chlorine-azide exchange reaction.
13,14,15
R N CI R2N)P=N -P
